finished second in the 2016 overall points standings. Rydquist capped off 2016 with another drive in the 25 Hours of Thunderhill, with the same team and car he had races in the NASA endurance season. Racing with former top 3 finishers Mike Holland, Beau Borders and Troy Lindstrom, Rydquist and the team's main competitors were Flying Lizards Porsche 997 GT3 RSR and Audi R8 GT3 LMS, as well as a Lamborghini Super Trofeo campaigned by CLP Motorsports. Halfway into the race Rydquist and his teammates were running 3rd in the ES (GT) class, however their chances to take a podium finish were eliminated when the front-splitter failed. Later in the race a rear balljoint failure dropped the team out of contention of even a top 10 finish. Rydquist's 2017 NASA Western Endurance Racing Championship season started off with a gearbox failure that dropped Rydquist from a one lap lead to an early end of his race, which put an immediate dent in his second NASA endurance title attempt. He followed up with back to back wins in the second and third rounds that both took place at Buttonwillow Raceway. With no means to recover enough championship points from the first race retirement the team exited the championship early to focus on winning the United States Touring Car Championship and to prepare for the 2017 25 Hours of Thunderhill. In 2017 Rydquist won the United States Touring Car Championship title, in the Grand Touring (GT) class. This extended the successful collaboration with the Prototype Development Group beyond endurance racing into Sprint Racing. Rydquist raced the team's Factory Five Racing GTM. He took the GT class and overall win at the season opener, a rain race at Laguna Seca. He then went on to claim second place at Auto Club Speedway before winning again both at Sonoma Raceway and at the series' second visit to Laguna Seca. Rydquist capped a very successful 2017 racing campaign together with the Prototype Development Group and team-mates Mike Holland, Beau Borders and Troy Lindstrom by claiming a 3rd place finish in his class (ES/GT) and 5th overall in the 2017 25 Hours of Thunderhill. In 2018 Rydquist once again entered the NASA Western Endurance Racing Championship, this time in the ESR class. His first entry of 2018 was with the Prototype Development Group's notorious Factory Five Racing GTM at the 3rd round held at Buttonwillow Raceway.